DESCRIPTION: (Applicant's Abstract) Previous research from this laboratory has demonstrated that the environmental circumstances surrounding amphetamine administration can powerfully modulate both its acute psychomotor activating effects and the ability of repeated amphetamine to induce behavioral sensitization. The purpose of the experiments described in this proposal is to examine, using immediate early gene expression as a marker of neuronal activity, the neural systems involved in the environmental modulation of both the acute and repeated effects of amphetamine. Specifically, we hypothesize that 1) the neural circuitry engaged by acute amphetamine will vary as a function of the environment in which it is administered, 2) the neural circuitry engaged by amphetamine will change as a function of prior drug history and the development of sensitization, and these neuroadaptations will vary as a function of the environment in which drug is administered, and 3) that mere exposure to contextual stimuli associated with prior drug administration will engage similar neural circuitry as that engaged by exposure to the drug itself. These experiments will provide important new insights into how the neurobiological actions of amphetamine are modulated by the environmental circumstances surrounding its administration.